Magnetic fishing tool



Dec. 22, 1959 C- W' COFFEE MAGNETIC FISHING TOOL Filed May 26, 1958 f 2,918,323 Ice Patented Dec. 22, 1959 2,918,323 MAGNETIC FISHING rroor. cnanesw. cpffee, Lubbock, rex. Application Mayv26, 1958, Serial No. 737,944 4. (C1- 29H55) 1 Ihis'invention pertainstomagnetic shing tools and, more particularly, to those tools designed to be lowered into! oilf well bores to retrieve: small parts of various junk which 'may be there.

' `An object -ofv this invention is to provide a magnetlc t'shingftool whichl producesA considerable turbulence of ciriculatingffluid to agitate the pieces of junk against the magnet.

.'Fu'rther objects are to achieve the above with a device that is sturdy, simple and" reliable` yet cheap and easy. to manufacture.

The specific nature of the invention as well as other objects, uses and advantages', thereof will clearly appear from the following description and the accompanying drawings in which:

Fig. 1 is a sectional view of a tool in accordance with this invention, as taken on line 1 1 of Fig. 2.

Fig. 2 is a cross sectional View taken on line 2 2, Fig. 1.

Fig. 3 is a cross sectional view of the tool taken on line 3-3 of Fig. 1.

Fig. 4 is a cross sectional view of a modification taken on a plane similar to the plane of Fig. 3.

Fig. 5 is across sectional view of another modification taken on a plane similar to the plane of Pig. 3.

An embodiment of this invention as shown in the accompanying drawings is somewhat simil-ar to the tool as disclosed in the U.S. patents to Kirby #2,668,077 and #2,790,116 and to Trowbridge #2,729,494. y

The tool has a cylindrical connector 10, which is threaded at its upper end to be connected to a string of drill pipe. There is a cylindrical axial bore for the passage of tiuid from the drill pipe to the working area. On the lower end are threads for the connection of tubular body 12. The lower end of the tubular body has external threads for connection of rotary shoe 14. Tubular body 12 has internal threads on its upper end both for the purpose of connection to connector and for securing upper pole plate 16 which is threaded along its edge to mate with the threads of the tubular body. The upper pole plate 16 is a disc of paramagnetic material. It has aperture 18 through the center for the passage of fluid.

Within tubular body 12 there is an upright elongated mass of magnetic material 20. The upper end of this mass of magnetic material is a plane surface, in contact with the upper pole plate 16, and normal to the axis of the tool. The lower end of .this elongated mass of magnetic material is also a plane surface which is parallel to the upper surface. Lower pole piece 22 is in contact with the lower end of the magnetic material 20 and approximately the same width. The lower pole A piece is likewise comprised of a paramagnetic material.

As taught in the Trowbridge patent, it should be of a tough material.

The mass of magnetic material 20 has fluid pass-age 24 from end to end thereof. This fluid passage is coaxial with the tubular body 12 and therefore registers with the passage through the connector 10 and upper pole plate 16. Pole piece 22 hask a` concave depression 23 in its contacting face which registers with the liuid passage` 24. A plurality of fluid passages 26 diverge from, this depression. They extend downward and outward tor apoint on the surfaceof the lower pole piece which is adjacent to the lower face. Considering the uid passages 2,6 as seen in Fig. 2 which is in a plane ofthe contacting face, it will be noted that they do not extend radially, They extend in an oblique direction from the central area, i.e. semitangential from depression 23. ln this manner. the liuid pumped through the fluid passages impinges with a greater degree of turbulence around the teeth of.A the rotary shoe. This aids in agitating whatever junk may. be in the bottom of the well so it is more readily attached to the lower face of the lower pole piece 22. As: seenin the, drawings, I prefer to have the diverging tluid passages angle generally in the direction of; rotation of the tool as evidenced by the teeth of the rotary shoe 14.

As mayY be seen in Fig. 3, acylindrical permanent magnet may be used with a circular bore therethrough. Since many of the better magnets arel presently made from extremely hard and brittle materials, the bore may be formed by the process of sonic vibrations ina slurry of abrasive material sometimes known as the Cavitron process. j

Because of the difliculty of machining magnetic materials a modification of the mass. of magneticV material is shown in-Fig. 4.` In this modiication the magnetic material is made up of two prisms 30 which have a D- shaped end or base. The two D-shaped prisms are separated by two rectangular prisms 32. The width of these rectangular prisms is less than one-half the cord lengths of the D-shaped ends. This leaves a central aperture 34 for the passage of fluid through the magnetic mass. The rectangular prisms 32 may be of magnetic material themselves. Then the permanent magnet also includes the rectangular prisms 32. Of course, having four elongated magnets all having their north poles adjacent and south poles adjacent will cause a repelling force between the four magnets. However, this aids in holding the magnetic material in the tubular body 12 a-s will be explained later. Of course, it is not essential that the prisms 32 be of magnetic material. They can be constructed of non-magnetic material as taught by Trowbridge.

Fig. 5 illustrates a further modification. ln this moditication, a magnetic mass is made up of eight rectangular prisms. Four of these rectangular prisms 40 are squarebased while the other four 42 are not. These particular configurations have been chosen as they most nearly till the circular space within which it is most convenient to coniine the magnetic mass, yet leave room for aperture 44 through the center for the passage of fluids, and also provide for the use of shapes which are easily formed from the magnetic material which will be used.

To assemble the device as shown in Fig. 5, I choose to first arrange the prismatic magnet-s in the unmagnetized state. A block of wood may be positioned in the aperture 44 to hold them in place temporarily. The magnets are securely strapped by metal bands 46. Then they are subjected to a high intensity unidirectional magnetic field to magnetize them so that all of their north poles are adjacent. This magnetization will cause each of the magnets to repell the others so that they tend to radiate from the central aperture 44. This makes it possible to easily remove -the wooden block from this aperture. Also, they are held securely in place as they tend to stretch out against the metallic bands 46. Then, using wooden poles as rails, the magnetized mass may be inserted within the tubular body 12 which already has the upper pole plate 16 in place. It is necessary to use nonmagnetic rails around the magnetic mass; otherwise, if the magnetic mass ever touches the tube 12, it is difiicult 22 is placed in position. The annular space betweenthe magnet and the body may be filled with Babbitt 28 or any other diamagnetic material that has a low melting point. Also, certain plastics may be used, such as epoxy resins. It is necessary that the temperatures not be extremely elevated in filling this space because of the adverse effect upon the magnet. At the lower end of the assembly the ller material 28 in the annular space between the magnet and the tubular body 12 is removed to a conical form as seen at 29. This provides the iinal passage for the uid which comes through the connector 10, magnetic mass 20 and on out the pole piece 22.

Thus it may be seen that in the three embodiments of Figs. 3, 4,. and 5, I have provided a tool wherein there is a lower annular magnetic pole around and concentric the magnetic pole in pole piece 22. The magnetic ux path extends from the pole piece 22 through the magnetized magnetic mass, through the upper pole piece 16, and through the tubular body 12. There is no closed magnetic path or short circuit (absent junk) because the pole piece 22 is isolated from the opposite concentric pole by diamagnetic material 28.

It will be apparent that the embodiments shown are only exemplary and the various modifications can be made in the construction, materials, and arrangement within the scope of the invention as dened in the appended claims.

I claim as my invention:

1. A magnetic fishing tool for operation on a string of drillpipe, comprising: an upright elongated mass of magnetic material having a uid passage therethrough, said passage extending from end to end, a north pole at one end of the mass and a south pole at the other, a lower pole piece contacting the lower end of said mass, said pole piece having diverging fiuid passages extending from an area on the contacting face which mates the iiuid passage of the mass, and means for connecting said mass to a drillpipe.

2, The invention as defined in claim 1 wherein the lower pole piece has a plane contacting face and the uid passages in the lower pole plate extend obliquely from a central area on the contacting face when projected to said plane.

3. The invention as dened in claim l wherein the mass of magnetic material includes a plurality of prisms; each of which has an upper base in a common plane and a lower base in a common plane, this being the contacting plane; and each prism being magnetized so 'that the north poles `are adjacent.

4. A magnetic fishing tool comprising: an elongated mass of magnetic material, said mass comprising a plurality of prisms of magnetic material, each prism having an upper end in a common plane and a lower end in a common plane, each prism being magnetized so that the north poles are adjacent, said prisms arranged so that there is a central fluid passage from end to end, and means for binding the prisms together against the natural magnetic repulsion.

No references cited. 

